1. Field of the Invention
The present invention relates to the gelation or viscosification of hydrocarbon fluids, wherein a polymer having the structure xB-[AB].sub.n -yA wherein the A block is hydrophobic and the B block is hydrophilic, n is an integer .ltoreq.1, x and y are 0 or 1 and y is 1, when n is 1 is mixed with an aqueous phase at a critical concentration level of about 0.001 to about 5.0 grams of polymer per 100 ml. of the aqueous phase, more preferably about 0.01 to about 3.0, and most preferably about 0.01 to about 1., thereby obtaining a turbid suspension of the polymer in the aqueous phase; adding with stirring about 0.1 to about 15.0 wt.% of a cosolvent to the turbid suspension, more preferably about 2.0 to about 15.0, and most preferably about 5.0 to about 15.0 to form an opalescent solution; stirring the opalescent solution for a sufficient period of time to insure the formation of a uniform polymeric solution; adding the polymeric solution to a hydrocarbon liquid; and stirring for a sufficient period of time the mixture of polymeric solution and hydrocarbon liquid until phase separation occurs, wherein the hydrocarbon layer is a cloudy, viscous pseudo-emulsion and the aqueous phase is clear and nonviscous.
2. Description of the Prior Art
There are many applications for very viscous or gelled solutions of polymers in organic liquids which are quite diverse. There are also a number of physical and chemical techniques for preparing such systems. The present invention is concerned with a process for converting a relatively low viscosity organic liquid solution into a very viscous or gelled system via a rapid process which, under certain conditions, can be reversed.
The mechanism of gelation of the hydrocarbon phase, as defined in the instant invention, occurs by the formation of macroscopic, spherical, nonionic polymer membranes or films dispersed throughout a continuous hydrocarbon phase, wherein large volumes of the hydrocarbon solvent of the hydrocarbon phase are encapsulated within a series of minute polymer bags (i.e., pseudo-emulsion system).
The instant invention differs from a number of applications, Ser. Nos., 374,251; 374,197; 374,198; and 374,252, filed by D. G. Peiffer et al, one of the instant inventors. These previously filed applications were directed to the thickening (gelling) of an aqueous fluid by a water-insoluble, neutralized, sulfonated ionomer.
The potential applications for this process and the products derived therefrom will be evident in the instant application. Some of these applications are: for the formulation of greases; for the formulation of caulking materials; for the viscosification of paint removers; a process for forming a jellied gasoline; a method of solidifying and stabilizing unstable sand or soil formations such as shale; a process for solidifying low viscosity hydrocarbons as a means for cleaning up oil spills; and a process for viscosifying oils.
The viscosification of hydrocarbon fluids (gasoline-type fuel, jet fuel, hexane, heptane, decane, paraffinic oils, etc.) is normally achieved by the addition of moderate amounts of high molecular weight polymers. The degree of viscosity increase is dependent on the level of polymer additive as well as the polymer molecular weight. As a consequence, the achievement of high viscosity via this approach requires either very high levels of additive or extremely high molecular weights of the additive component. Either of these approaches very often has some marked disadvantages in that high levels of additive are often uneconomical, and the use of very high molecular weight additives gives rise to shear degradation and/or oxidative degradation which means that viscosities obtained are often unstable. In light of these problems, there is a need for alternative techniques that would provide substantial hydrocarbon fluid viscosification at much lower additive levels and with lower molecular weight components. There are a number of potential advantages via this approach such as improved economics, higher levels of viscosification, and less contamination of the hydrocarbon fluid by the additive.
The instant specification describes an approach using a specific class of polymers which permits viscosification of hydrocarbon fluid which is an oil-in-oil pseudo-emulsion stabilized by a polymer membrane suitably solvated at the interface.
In order to achieve this "oil-in-oil pseudo-emulsion", it has been observed that a polymer is required which is multiphase, containing a substantially hydrophilic block coupled with a substantially hydrophobic block. Under normal conditions, such a block copolymer would be phase separated and when immersed in water could provide an aqueous suspension, wherein the hydrophilic block is highly water soluble. If one places such a polymer in an aqueous phase at high polymer levels, i.e., 5%, essentially a water solvated gel results as described in U.S. Pat. No. 4,130,517. If one employs the polymer at a much lower level, i.e., 1%, then a turbid suspension is obtained, the exact nature of which depends on the specific polymer, the molecular weight, and its composition. The addition of a modest level of cosolvent (i.e., a solvent for the hydrophobic phase such as tetrahydrofuran) results in an improved solution, presumably because of preferential solvation of the hydrophobic phase.
The addition of a substantial volume of a hydrocarbon fluid to an aqueous solution of this preferred class of polymers accompanied by modest agitation results in substantial surface activity and the immediate formation of a very viscous hydrocarbon phase which appears to be an oil-in-oil pseudo-emulsion. The aqueous phase now appears as a nonviscous water layer. The viscosity is directly attributed to the large volume of the hydrocarbon solvent of the hydrocarbon phase encapsulated within a series of minute polymer spheres.
There are a broad class of polymers which could perform the function described above, and the preferred systems are described in U.S. Pat. No. 4,130,517. An especially preferred block copolymer is that with a hydrophilic block based on polyethylene oxide and the hydrophobic block based on polystyrene. There are a number of such polymer structures that can be prepared, but for the purpose of this invention and their structures, can be referred to as (AB).sub.n or ABA where the A block is hydrophobic and the B block is hydrophilic. To be applicable for the instant invention, these materials would have preferably 50% of the polymer composition existing as a hydrophilic block (B block), although one can reduce this content down to 30% and still have an effective polymer system. It is also contemplated that polymers of at least 3 blocks are most preferred because they develop the required solubility characteristics and membrane strength characteristics desired for optimum performance.
The viscosification of hydrocarbon fluids has a very important technological objective currently demanded of hydrocarbons employed in greases, oil additives, drag reduction areas, demisting applications, oil well drilling, and oil well workover applications. Typically, polymer levels on the order of 1% up to 5% are required to be effective in these areas. Substantial viscosification can be achieved at 100 to 5000 parts per million of polymer additive; in the instant invention, this is a very substantial reduction in the amount of additive necessary for effective viscosification. It is anticipated that these fluids viscosified as described above will be useful in drag reduction applications, i.e., reduction of power required to drive a hydrocarbon fluid through an orifice; in the viscosification of jet fuels where there is a high level of interest in obtaining jet fuels which will not readily create a mist or vapor capable of explosion or combustion when such air craft are involved in accidental impact.
The instant invention differs from U.S. Ser. Nos. 106,027 (now U.S. Pat. No. 4,282,130, issued Aug. 4, 1981); 136,837 (now U.S. Pat. No. 4,322,329, issued Mar. 30, 1982); and 223,482 (now U.S. Pat. No. 4,361,658, issued Nov. 30, 1982) in that these aforementioned applications are directed to the gelation of hydrocarbon liquids by neutralized sulfonated thermoplastics, whereas the instant invention is directed to a class of unsulfonated polymers used as viscosity modifiers. In addition, the instant invention differs from a number of applications, Ser. Nos. 374,197; 374,198; 374,251; and 374,252, filed by D. G. Peiffer et al, one of the instant inventors. These previously filed applications were directed to the thickening of an aqueous fluid by a water-insoluble, neutralized sulfonated isomer.